The present invention relates to a circuit breaker, and it relates, in particular, to a fluid pressure operating apparatus for such the circuit breaker, being suitable as a circuit breaker for use of electric power.
An example of a conventional fluid pressure operating apparatus for use in a circuit breaker is shown, for example, in Japanese Patent Laying-open No. 2000-90784 (2000) <JP-A 2000-90784>. Such the operating apparatus as described in this publication has a piston for use of opening/closing of a contact, for the operating apparatus to bring the contact into open/close, and a control valve mechanism for actuating this, for preventing the contact from a pumping operation of repeating opening/closing operation thereof. The control valve mechanism has a switching valve and a switching control valve. The directional valve changes over the pressure onto a cylinder operation chamber of a piston for use of opening/closing of the contact. The switching control valve has a switching control valve for use of close (operation) and a switching control valve for use of open (operation). There is provided an anti-pumping piston for closing a check valve, and a conduit is connected to an anti-pumping piston operation chamber, which is branched from a portion between a secondary side of the switching controller valve for use of close (operation) and a primary side of the check valve.
In such the fluid operating apparatus as described in the Japanese Patent Laying-Open No. 2000-90784 (2000) mentioned above, a solenoid drives a pilot valve, and the pilot valve drives the directional control valve, respectively. And, the directional control valve operates a main valve for use of open (operation) and a main valve for use of close (operation). As a result of this, for actuating the piston for driving the contact, the valves are necessary in a large number thereof, thereby bringing about a large-size of the apparatus, as well as, a large number of parts thereof. Also, since the fluid flows directly into a return side of low pressure from a supply side during the operation of the directional control valve, this may be a factor of causing pressure fluctuation, and therefore it is strongly desired to reduce that.